The present invention relates to a device and method for detecting a motion amount from a video signal, and a luminance/chrominance signal separation device and method, a noise reduction device and method, and a video display device and method adopting the motion detection device and method.
In recent years, as TV receivers have been upsized and enhanced in image quality, higher importance has been increasingly placed on enhancing the performance of a luminance/chrominance signal (Y/C) separation device that separates a luminance signal and a chrominance signal from a composite video signal. In a type of luminance/chrominance signal separation device called a three-dimensional YC separation device, switching between two-dimensional YC separation using line correlation and three-dimensional YC separation using frame correlation is made according to the results of motion detection. Therefore, high importance has also been placed on enhancing the performance of a motion detection circuit.
A conventional motion detection device and luminance/chrominance signal separation device will be described.
FIG. 20 is a block diagram of a motion processing circuit disclosed in Japanese Laid-Open Patent Publication No. 10-108039. Referring to FIG. 20, an input composite video signal S1100, as a current frame signal, is sequentially supplied to a frame memory 1101 and a motion detection circuit 1102, and also to a first edge detection circuit 1103. The frame memory 1101 holds the current frame signal for one frame period and then supplies the signal as a one-frame preceding frame signal S1101 to the motion detection circuit 1102 and a second edge detection circuit 1104. A determination circuit 1105 is composed of an AND circuit for calculating logical AND of the inputs from the first edge detection circuit 1103 and the second edge detection circuit 1104. An adaptive processing circuit 1106 attenuates a motion signal S1102 according to a signal S1105 output from the determination circuit 1105.
The operation of the motion detection device configured as described above is as follows.
FIG. 21 represents a situation of the motion processing circuit shown in FIG. 20 in which the input signal S1100 includes an edge portion and the edge portion has shifted from the position thereof in the one-frame preceding signal S1101. The motion signal S1102 output from the motion detection circuit 1102 indicates that the edge portion has shifted. The first and second edge detection circuits 1103 and 1104 respectively detect the edge and output edge detection signals S1103 and S1104. Since the edge portions of these signals do not overlap each other, the determination circuit 1105 outputs 0 as the determination signal S1105. With the determination signal S1105 of 0, the motion signal S1102 is output as it is as a signal S1106.
FIG. 22 represents another situation of the motion processing circuit shown in FIG. 20 in which the input signal S1100 contains an oblique component. The motion signal S1106 is output in the manner described with reference to FIG. 21.
However, the motion processing circuit described above fails to distinguish the case of input of an oblique portion from the case of input of an edge portion in the detection of an edge portion. Therefore, the conventional motion processing circuit is not allowed to correct or attenuate the motion amount as the motion detection results when an oblique component is input.
When the motion processing circuit described above is applied to a type of luminance/chrominance signal separation device in which switching between two-dimensional YC separation using line correlation and inter-frame YC separation using frame correlation is made according to the output signal of the motion processing circuit, it is not allowed to perform switching between the line correlation and the frame correlation according to the amount of oblique components. In other words, it is not allowed to attenuate the motion amount so as to be determined as being “still” or change the threshold for motion determination when the signal contains an oblique component. In this situation, when a signal containing a large amount of oblique components is input, it is not possible to reduce cross-color, which occurs due to mixing of a luminance component into a chrominance component during separation of a luminance signal and a chrominance signal from a composite video signal.